Process for making alpha, alphathiodialiphatic acids



Patented Feb. 22, 1949 PROCESS FOR MAKING ALPHA, ALPHA- THIODIALIPHATIC ACIDS Milton P. Kleinholz, East Chicago, Ind., assignor to Sinclair Refining Company, New York, N. Y,, a corporation of Maine Nolllrawing. Application Sept-ember 6,1945, Serial No. 614,817

7 Claims. 2.

The prese t nventionr lates t t e p od of alpha, alphat-thiodialiphatic acids and of mixures consisting principal y of alph a ph hi ialiph ti acid and of alpha-hvdr y liphatic acids, from which the former in relatively pure form may be readily obtained when desired.

Theinvention provides an improved process for the production of chemical compositions consisting principally of alpha, alphaf-thiodialiphatic acid and 'alpha hydroxy aliphatic acid.

The process is applicable to the production of mixtures of such derivatives of various fatty acids, for instance stearicacid, palmitic acid, myristic acid and lauric acid, but has been found to be particularly advantageousin the production R-OH-OOOH and Where R. isan aliphatic group containing 10 to 16 carbon atoms.

.In general, the process of my present invention comprises reacting an alpha-brominated fatty acid, corresponding to the product d sired and of the group consisting of stearic acid, palmitic acid, myristic acid or lauric acid, or mixtures thereof, in benzene solution or methyl alcohol solution, butpreferably in benzene solution,

with potassium hydroxide, to neutralize the :aciditycfthesfattyacid, thereafter reacting the "resultant potassium soap with sodium sulfide in aqueous. solution, acidifying the mixture with a mineral acid, for instance hydrochloric, and separating the resultant admixture of alpha, alphathiodialiphatic acid and alpha-'hydroxy aliphatic acid from the solution. When desired these acid derivatives may subsequently be separated by known methods, for instance by re-crystallization. Either a crude or a crystallized alpha-brominated aliphatic acid may be used as the starting material. For my purpose I have used alphadesirable.

m at d al phatic cids on a ng. or i stance, from about 2 4% to about 30% of bromine,

The process is with advantage carried out in a kettle. equ pp wit a s irr r. nd l ned ith glass ora similar material capable of resisting the corrosive action of the reactants employed.

The a p br m0 acid. f r instance. may be prepared by reactinglauric acid with bromine in the presence of red phosphorus, as will be more fully described hereinafter.

It has previously been propesed that thiodicarbo ylic acids ay b pre ar d y a pro esscomprisin reactin a chlorin te fa ty acid wit a al a i m t l su fideli wever, 01 method ha been found to result in a product having inferior rust inhibiting properties, even after recrystallization, probably due to sulfur linkages other than in the alpha position, or incompletereaction of the chlorinated compound with the sodium sul:

fide, or perhaps a combination of such results g I have found that by using alpha brominatedfatty acid instead of the chlorinated compound,

and by reacting said brominated fatty acid withv potassium hydroxide to form the potassium soap prior to reaction with the sodium sulfide, the physical characteristics of the reaction mass are materially changed, and thereby a more rapid and complete reaction with the sodium sulfide is obtained.

A further highly desirabl'easpect of my present invention is the reacting of the resultant potassium soap-benzene solution with the sodium sulfide in aqueous solution, as this procedure appears materially to affect the purity of the product and to lessen the tendency toward the production of undesirable products such as mercaptoaliphatic acids.

It is usually desirable that residual bromine.

present in the finished product intended for use as a lubricating oil addend be reduced to'not in exceess of about 0.5%. A further advantageous aspect of my present invention is the effective means of accomplishing this end when In accordance with my present process I may substantially eliminate the residual bromine content. To accomplish this, I prefer to distill the benzene from the product resulting from the reaction with sodium sulfide and thereafter to digest the said reaction product for an additional period with potassium hydroxide. The removal of the benzene prior to this further digestion period has been found materially to facilitate the desired reaction.

By my improved process, one is enabled consistently to obtain a uniform product substan- .salt. ture was settled to permit the separation of the tially free from objectionable reaction products, the product being a mixture of the alpha, alphathiodialiphatic acid and alpha-hydroxy aliphatic acid containing about 20 to 50% of the latter constituent, which mixture has been found to be a highly effective rust inhibitor.

The alpha-bromolauric acid used in the process of my present invention has been successfully prepared as follows:

200 grams (1.0 mole) of distilled lauric acid, containing about 30% myristic acid, and having an acid number of 268, was placed in a B-necked flask with 10.3 grams (0.33 gram-atom) of red phosphorus and this mixture was heated to 170 F. 240 grams (1.5 moles) of bromine was then slowly added over a period of two hours, after which the mixture was heated slowly to 195 F. for an additional 5 hours and the mixture permitted to cool. The cooled mixture then was blown with air to remove unreacted bromine and then diluted with 280 cc. benzene and washed twice with 150 cc. portions of water at 140 F. After the aqueous layer had been separated by settling, the benzene layer, which contained the alphabromolauric acid, was filtered. The product separated from a portion of this benzene solution was found to have an acid number of 203 and to contain 24.2% bromine.

The procedure which I have found most desir able, especially in the preparation of mixtures of alpha, alpha'-thiodilauric acid and alpha hydroxy lauric acid with a low bromine content, is illustrated by the following example:

Example I 1420 grams (5 moles) of alpha-bromolaurlc acid, prepared as previously described from a commercial fatty acid of 8 to 18 carbon atoms per molecule, was charged to a 5-gallon glass-lined Pfaudler kettle equipped with a water jacket, stirrer, thermometer and condenser. A total of 6,000 cc. of benzol was then added, and the stirrer started. 280 grams (5 moles) of potassium hydroxide in 420 grams of water was then added over a period of a minute at an initial reaction ,temperature of 80 F. Stirring was continued ,for' a total of five minutes to allow the reaction with the potassium hydroxide. A solution of 780 grams of Na2S.9H2O in 1170 grams of water was then added and the mixture was heated over a period of one hour to a temperature of 160 F. and held at this temperature for 12 hours with stirring. The stirrer was then stopped and the benzene and aqueous phases allowed to separate by standing for a period of one hour. The aqueous phase was discarded, and the benzene phase topped to a maximum bottom temperature of 212 F. to remove benzene.

At the end of the reaction period above described, the potassium salt of the thiodilauric acid was found to contain about 2% bromine. V In order to reduce this bromine content, there was added .to the reaction mixture from which the benzene'has been removed, 7500 grams of a 1% potassium hydroxide solution. The mixture was heated slowly to 200 F. and the retreatment with potassium hydroxide continued for 8 hours. The

reaction mixture was then cooled and benzene and excess hydrochloric acid added to acidifythe After a one-hour reaction period the mixaqueous phase and the benzene phase. The aqueous phase was discarded and the benzene phase was again washed with-acid and then with water. After again separating the aqueous phase,

the benzene was topped off from the benzene phase and the residue stripped by blowing with steam at 200 F. maximum bottom temperature. The residue was then blown with air for 15 minutes to remove any condensed moisture, and the hot stripped product was finally filtered, and found to contain 4.90% sulfur and 1.02% bromine,

By the retreatment of the intermediate reaction product with potassium hydroxide prior to acidification, the bromine content of the product may be reduced to a minimum. Such retreatment removes substantially all of the bromine, where the acid from which the alphabromoacid was prepared was substantially free from unsaturates. Even where unsaturates were present in the raw material, all but an unobjectionably small amount of bromine may be removed. Such retreatment of the intermediate reaction product for the removal of bromine is preferably carried out in aqueous solution in the substantial absence of benzene or methyl alcohol.

By the process of the present invention alpha, alpha-thiodilauric acid of suitable purity has been prepared from alpha-bromolauric acid containing as little as 24.1 to as high as 30.7% bromine. Suitable alpha, alpha-thiodilauric acids have been prepared from crude fatty acids containing from 8 to 18 carbon atoms per molecule and also from substantially pure lauric acid. Alpha, alpha'-thiodilauric acid, prepared as described, has been found to contain from 20 to 50% of alpha-hydroxylauric acid.

For some purposes, the presence of the alphahydroxylauric acid in the alpha, alpha-thiodilauric acid product is not objectionable and may actually be desirable. For instance, when used as an anti-rusting agent in a turbine oil, the presence of alpha-hydroxylauric acid has been found to incrase the effectiveness of the alpha, alphathiodilauric acid.

The tendency toward the formation of alphahydroxylauric acid is increased where the original neutralization of the fatty acid is not promptly followed by the addition of the sodium sulfide. Thus, where it is desirable to increase the proportion of hydroxylauric acid present in the product, this may be effected by an appropriate modification of the process.

It has been found particularly desirable, in carrying out the process of the present invention, to maintain the reaction temperature following the addition of the sodium sulfide at about 155- 160 F. At this temperature, the major portion of the reaction has been found to have been effected in about four hours. Higher temperatures may be employed, for instance up to about 200 F., but at the higher temperature objectionable foaming is likely to be encountered. Also, to effect a clean separation of the aqueous phase from the organic phase, it is desirable to settle the mixture at a temperature of about 130-140 E.

The process of my present invention will be further described and illustrated by the following specific examples of its application to-the production of mixtures of alpha, alpha-thiodistearlc acid and alpha-hydroxy stearic acid. For completeness, an advantageous method for the pro- 7 duction of the alpha-bromostearic acid used in the operation is also included.

" "Example II bromine:- addition number...

5% of*"50.% palmitic acid, 41%: stearic. acid} and? 9% 'oiei'c acid"; Inthe-preparationof the bromostearic acid". 807grams (3.0 moles) oithe steariczacid and 4023 grams: (1.3 gram-atoms) of red: phosphorus were well" mixed together a: 3-liter, 3-necked flask provided with a thermometer, a dropping funnel, a reflux condenser, and a bromine and hydrogen bromide gas trap. This. mixture was heatedon asteam bathuntil' there was obtained a molten massofi the stearic acid with: the.:'phos:-

phorus suspended therein; At this point-13.61 gram (8.5 moles) of bromine was added over a. period of2 /2hours: The heating was continued for an additional. three hours at 200 F. and the mixture Was then permitted to'starid overnight. Inthe morning the; crude: alpha-bromoacidbro.- mide was'pouredinto two liters of cold water and warmed gently to-convert. it to the alpha-bromoacid; The; crude product thus obtained was washed several; times with water to remove hydrogerr. bromide. The resultant product. formed a. butter-likemass; which was dissolved in. a mixturesof hotbenzokand naphtha. The material was then: settled to permit separation of an aqueous-phase and. the organic phase; organic layerwasthen washed several times with water; filtered, and allowed to-stand-inan evapo- Thev rating: By this procedure there-was obtained 7 577 grams-of. crystalshaving an acid; number of 1.5.5.6 and: containing 26.07% bromine.

A mixture of alpha, alphathiodistearie acid and alpha-hydroxy steari'c'acidwasprepared from the alphau-bromostearic acidthus producedby'the following procedure:

72 grams (0.2 mole) of theralpha-bromostearic acid, prepared as just described, was dissolved in 200 cc. of methanol. in a 500'- cc. round bottom flask. There was thenadded in the cold 11.2 grams (0.2 mole) of potassium hydroxide dissolved in. 100 cc. of methanol to neutralize the? wbromoacid. Thereafter,48' grams. (0.2 mole) of sodium sulfide (NazSLQI-IzO'), dissolvedin '50 cc. of water, was rapidly addedin the cold. The reaction solution. turned a green black, and a heavy precipitate was deposited within ten minutes after the addition of the sodium sulfide; K. reflux condenser was then attached .and' the. reaction mixture was, refluxed for 1'6 hours. The precipitate was then filtered from the cooled reaction mixture, suspended in 500 cc. of. water; and acidified by the addition of 100' cc. ofi'concentrated hydrochloric acid; The

crude alpha, alpha'-thiodistearic.acid' thus formed ad'aptatio-n of the process girthpresent invention to large scale" plant operation isillus- 't'rat'ed" by'the following example or its use-in the production of crude alpha, alpha'thiodilauricacid.

In this operation the alpha-bromolauric acid was preparedfronra commercial lauric acid having an acid number of 282.7, a saponification number of 297.4, containing no sulfate-ash, and'having a 'zero .500 lbsof the lauri'c. acidwas placed in 90500 gallon; glass -lined P'faudler kettlaprovided with a absorption. tower. .25. pounds: of: red; phosphorus acid.

was also added to'the kettle. 8110.' 11384.01; bromine was then added to the molten. acid andred phos. phorus overxa. periodof: /2 hours, during which time the temperature of the; mixture ranged; lee-.- tween; 150 15.; and 170 Fl. The reaction is: ex?- oth'ermi'c", and cooling: was. required. After the bromine-had been introduced, the temperature of the mixture was. raised to 200 F. overa period-of an. hour' and; maintained at. that temperature for four hours. Thereafter the reaction mixture. was cooled and? permitted; to: stand; overnight. The following. morning: 3+4 gallons of syrupy'acid of phosphorus was drawnofi. and the reactionsmixeturez: was. blown with air: for anhour. The bromoacid .bromiderwas-then: dissolved in 100 gallons of dry benzol by. agitating with air for minutes, filtered; through a Schriver press into a. second kettlecontaining .90 gall'onsof water; The kettle, press and lines-were then-washed with 80 gallons of. benZol and this wash. liquor combined with the filtered-,benzol solution. The mixture was stirred at .atemperatureof 145 F. for onehounandithen,

settled: After: oneqhour. ofsettl'ing, anorangeQ-red water layer was formed and: was drawn offyand the benzol. layer. containing the: bromoacid was washed for one; hour with? 50:gallons:of water at 140 F. and then permitted. to settle for several hours. The resultant alpharbromolauric acid was found: to contain 26.3% bromine, as against" a theoretical bromine content of 28.1, indicating that 9316% of the, theoretical bromin'ation had been efiected.

After settling, the aqueous layer: from: the second water wash was-edrawn-oiT-c and 180 gallons of benzol added; There was; then added to the solution 155 pounds of potassium hydroxide. in gallons of water over a period"; ofthree' minutes, with stirring.v At the end. of the addition. the temperature of the solution had risen to 102 F. Stirring was continued for 20- minutes, and. 39.0 lbs. of hydrated sodium sulfide in 72 gallons of Water was added over a period of 20 minutes, the temperature being maintained at 102 F. The temperature of the reaction mixture was. then. gradually raised to 155 F. over a period of one hour and maintainedat that temperature for eight hours with stirring. The mass was then settled for an hour, and gallons of dark green aqueous phase was drawn off. A sample of acids separated from the resultant reaction mass was found to contain 0.37% bromine.

30 gallons of water was then added and all of the benzol' present was topped off over a period of 2 hours at a bottom temperature of 193 F. 350 gallons of water and pounds of potassium hydroxide in 25 gallons of water were then added. Stirring was discontinued and the reaction mass was carefully heated to 200 F. over a period of 5 2; hours soas to'preven-t foaming. The mass was held at aboutv 200 F. for "9 hours "and" at that time analysis 'of' a sample 'o'f"acid's' obtained from the mixture indicated the bromine content to have dropped to 0.13%. After 17 hours heating at: 200 Kathe bromine content dropped to 0.10% and after 33% hours the bromine content had dropped? to 0.07%.

The reaction mass was then cooled to 144 F. and 35.0cgallons of. benzol' added, followed by. the addition of 6.45 pounds of 36% hydrochloric The: mass was stirred for one hour and then settled for one: hour at; F. The aqueous. phase; was. then drawn on and the henaol' phase: againwasl'ied': with 645 pounds of the: hydrochloric acid; in; 1 50 gal19I1 i Water.

7 The mixture was stirred for two hours and settled for one hour at 130 F.

The benzol phase was then given two washings with 60 gallons of water each, the aqueous phase settled out and drawn 01f as before, and the benzol phase topped with stirring to a bottom temperature of 208 F. over a period of 1% hours. Live steam was then introduced into the product for 30 minutes to remove any remaining benzol, and the product was then blown with air at 200 F. to remove any dissolved Water.

5 pounds of filter aid was then added and the product filtered at 200 F.

By the foregoing procedure 505.3 pounds of 'crude alpha, alpha'-thiodilauric acid was obtained. The product was found by analysis to contain 0.07% bromine, 4.64% sulfur, 1.4% water, 0.03% sulfate ash, to have a specific gravity (77 F./77 F.) of 0.9989, a melting point of about 116 R, an acid number, cold, of 242, an .acid number, hot, of 273.8, and a saponification number of 275.8. The crude product was further found by analysis to contain a substantial amount of alpha-hydroxylauric acid.

The products prepared in accordance with my present process have been found to contain substantially no mercapto fatty acids.

Especially in large scale operation, it is particularly advantageous to use potassium hydroxide in the neutralizing of the alpha-bromonated fatty acid. The use of sodium hydroxide, for instance, results in the formation of stiff soap jells which are very difilcult to work. The potassium soaps form stiff jells which, though very viscous, are still quite manageable.

I claim:

1. A process for producing mixtures of alpha,

alpha'-thiodialiphatic acids and alpha-hydroxy aliphatic acids of the types represented respectively by the formulae ROHCOOH RGHOOOH and I OH R-CH-OOOH where R is an alkyl group, which comprises reacting an alpha-brominated fatty acid of the group consisting of stearic acid,

palmitic acid, myristic acid and lauric acid,

and mixtures thereof, in solution in an organic solvent of the group consisting of benzol and methanol, with potassium hydroxide by intimately admixing them, thereafter reacting the resultant mixture with sodium sulfide in aqueous solution by admixing and heating to a temperature of, '155-200 F., acidifying the mixture, settling to permit the formation of an organic layer containing the desired reaction product and an aqueous layer, separating the two layers and distilling off the organic solvents from the former.

2. A process'for producing mixturesof, alpha, alphaf-thiodialiphatic acids and alpha-,h'ydroxy aliphatic acids of the types representedres'pectively by the formlae a-orr-ooon and rc-orr-ooon OH where R is an alkyl group, which comprises reacting an alphabrominated fatty where R is an alkyl with sodium sulfide in aqueous solution by admixing and heating to a temperature of 155- 200 F., acidifying the mixture, settling to permit the formation of a benzol layer containing the desired reaction product, and an aqueous layer, separating the two layers and distilling oi! the benzol from the former.

3. A process for producing mixtures of alpha, alpha-thiodialiphatic acids and alpha-hydroxy aliphatic acids of the types represented respectively by the formulae R-OH-COOH R-oH-oooH S and A on R- H-COOH where R is an alkyl group, which comprises reacting an alpha-brominated fatty acidof the group consisting of stearic acid, palmitic acid, myristic acid and lauric acid; and mixtures thereof, in solutions of benzol with potassium hydroxide by intimately admixing them, thereafter reacting the resultant mixture with sodium sulfide in aqueous solution by admixing and heating to a temperature of 155- 200 F., acidifying the mixture by adding hydrochloric acid, settling the resultant mixture at a temperature of about 130-140" F. to permit the formation of a benzol layer containing the desired reaction product and an aqueous layer,

separating the two layers and distilling off the benzol from the former.

4. A process for producing mixtures of alpha, alpha-thiodialiphatic acids and alpha-hydroxy aliphatic acids of the types represented respectively by the formulae:

group, which comprises reacting an alpha-brominated ,fatty acid of the group consisting of stearic acid, palmitic acid, myristic acid and lauric acid, and mixtures thereof, in solutions in benzol with potassium hydroxide by intimately admixing them, thereafter reacting the resultant mixture with sodium sulfide in aqueous solution by mixing and heating to a temperature of 155-200" F., settling to permit the formation of a benzol layer and an aqueous layer, separating the two settling to permit the formation of a benzol layer containing the desired reaction product and an aqueous layer, separating the two layers and distilling oif the benzol from the former.

. .5. A process for producing mixtures of alpha, alpha'-thiodialiphatic acids and alphahydroxy aliphatic acids of the types represented respecprises reacting an alpha-brominated fatty acid of the group consisting of stearlc acid,

R-CH-COOH palmitic acid, myristic acid and lauric acid, and mixtures thereof, in benzol solutions with potassiurdhydroxide by intimately admixing them,

immediately thereafter reacting the resultant mixture with sodium sulfide in aqueous solution by admixing and heating to a temperature of 155-160 F., acidifying the mixture, settling to permit the formation of a benzol layer containing the desired reaction product and an aqueous layer, separating the two layers and distilling off the benzol from the former.

6. A process for producing mixtures of alpha, alpha'-thiodistearic acid and alpha-hydroxy stearic acid which comprises reacting alpha-bromostearic acid in benzol solution with potassium hydroxide by intimately admixing them, thereafter reacting the resultant mixture with sodium sulfide in aqueous solution by admixing and heating to a temperature of 155-160 F., acidifying the mixture, settling to permit the formation of a benzol layer containing the alpha, alphathiodistearic acid mixture and an aqueous layer, separating the two layers and distilling off the benzol from the former.

7. A process for producing mixtures of alpha, alpha -thiodilauric acid and alpha-hydroxy lauric 10 acid which comprises reacting alpha-bromolauric acid in benzol solution with potassium hydroxide by intimately admixing them, thereafter reacting the resultant mixture with sodium sulfide in aqueous solution by admixing and heating to a temperature of 155-160 F., acidifying the mixture, settling to permit the formation of a benzol layer containing the alpha, alpha-thiodilauric acid mixture and an aqueous layer, separatin the two layers and distilling off the benzol from the former.

MILTON P. KLEINHOLZ.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 20 2,279,734 Dreger et a1 Apr. 14, 1942 2,337,868 Burwell et a1 Dec. 28, 1943 2,369,640 Barnum Feb. 20, 1945 2,371,207 Zublin et a1 Mar. 13, 1945 

